Communication devices have traditionally been used to facilitate oral communication (e.g., talking) over a telecommunications network. However, non-oral communication remains important in today's society. For example, some people simply prefer texting over talking, while others, such as the hearing and speech impaired, may be physically unable to communicate orally.
Teletypewriter (TTY) technology was developed in the 1960's to allow the hearing and speech impaired to communicate using text over standard telephone lines. TTY was later implemented in wireless networks for use with mobile handsets, but as wireless networks evolved from a circuit-switched (CS) architecture to a packet-switched (PS) architecture, TTY technology became unsuitable for use in wireless networks, which are primarily based on Internet Protocol (IP) communications. This led to a decision by the Federal Communications Commission (FCC) to mandate that carriers replace legacy TTY technology with real time text (RTT) technology.
RTT allows for a near instantaneous transmission of text content between IP-based terminals. As a user of a source device types a RTT message, the text content of the RTT message is displayed on a destination device in real-time, without requiring the user of the source device to select a “send” button. This near instantaneous transmission of text content resembles a more natural conversation that is preferred by the hearing and speech impaired over traditional text messaging (e.g., Short Message Service (SMS) text). RTT also allows both parties of a communication session to type concurrently (e.g., allowing one user to interrupt the other user), and RTT can be implemented as an add-on to voice, which enables simultaneous voice and RTT media streams. However, technical limitations of RTT technology only allow text content (e.g., typographical characters) to be transmitted in RTT messages. Thus, if a sending user wants to send a digital photograph to another user, for example, the sending user is required to invoke a standard messaging application to send the digital photograph over the telecommunications network. This type of transmission can experience discernable latency due to the “store and forward” transmission technique of standard messaging services, and the relatively low Quality of Service (QoS) assigned thereto. Furthermore, because of RTT's newness, the networking implementations of RTT technology are rather limited today.